| yolk sac carcinoma | Malignant germ cell tumour commonly found in the ovary. The tumour arises from primitive germ cells and develops into extra-embryonic tissue resembling the yolk sac. Synonym: yolk sac carcinoma. (05 Mar 2000) |
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| yolk sac tumour | An unusual and aggressive tumour of germ-cell origin that reproduces the extraembryonic structures of the early embryo. It is the most common malignant germ cell tumour found in children. It is characterised by a labyrinthine glandular pattern of flat epithelial cells and rounded papillary processes with a central capillary (schiller-duval body). The tumour is rarely bilateral. Before the use of combination chemotherapy, the tumour was almost invariably fatal. (12 Dec 1998) |
| yolk stalk | A narrow tube present in the early embryo that connects the midgut of the embryo (through the umbilical opening) to the yolk sac outside the embryo. Later in development, the yolk stalk is usually obliterated but a remnants of it may persist, most commonly as a finger-like protrusion from the small intestine known as meckel's diverticulum. Found in 2-4% of people, meckel's diverticulum may become inflamed much like the appendix and require surgical removal. The yolk stalk is also called the umbilical duct, vitelline duct, or oomphalomesenteric duct. (12 Dec 1998) |